Precision pointing and positioning systems are widely used in telescopic systems making observations from space. The requirements on these systems are extreme. Their precision positioning requirements are extreme as are the extreme cold temperatures in which they must perform and the severe limitations of mass and available power.
Existing aerospace actuator technologies have not been adequate so new concepts have emerged, the “Inch Worm” [1] concept being one of the more popular. The “Inch Worm” concept was attractive because it could meet the extreme precision positioning requirements over long stroke distances, has low mass and power requirements and can hold position with power off. However, it used piezoelectric drive to gain precision and keep mass down and this did not perform properly in the ultra cold operating conditions of space so the “Inch Worm” concept remains unused, pending a work around.
Linear Tape Motors revisit the advantages in the Inch Worm approach, from fresh perspectives to overcome previous Inch Worm limitations, short comings and risk. It uses flexure bending to achieve small step resolution rather than piezoelectric expansion and magnetic drives to energize the flexures and hold position with power off. Flexures and permanent magnet electric motor drives work at ultra cold cryogenic temperatures and have extensive heritage in electric motor applications. Since Linear Tape Motor is just another electric motor form, much available technology can be used and since the innovative aspects are simple and straight forward there is reason to expect a short, inexpensive development phase with a certain, successful outcome.
The Linear Tape Motor concept was seen to have advantages in applications beyond its original purpose so the design concept was adjusted to incorporate these as well. The flexures and rare earth permanent magnets that work so well at cryogenic temperatures also work at room temperatures and above until they demagnetize at their (very hot) curie temperatures. Miniature space actuators scale up as required to handle large loads with safety and precision.